Nebriinae | uk beetles

NEBRIINAE Laporte, 1834

This group of typical carabids includes some of our most common and widespread ground beetles, as well as a few more localized specialist species.

ADEPHAGA Clairville, 1806

CARABIDAE Latreille, 1802

4.2-23mm

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Introduction

This is a mostly Holarctic group including about 12 genera in 5 tribes although the large genus Nebria Latreille, 1802 has been variously split into several genera, sometimes classified as subgenera, and so the number will vary in the literature. Notiokasiini Kavanaugh & Négre, 1982 includes the single species Notiokasis chaudoiri, Kavanaugh & Négre, 1982 from south-eastern South America, which is the only member of the tribe native to the Southern Hemisphere. The monogeneric Pelophilini Kavanaugh, 1996 includes 2 species of Pelophila Dejean, 1821; one Holarctic and one Nearctic. Opisthiini includes 2 genera; the monotypic Opisthius Kirby, 1837 is Nearctic while the 4 species of Paropisthius Casey, 1920 are Oriental. The Holarctic Notiophilini Motschulsky, 1850 includes about 50 species of Notiophilus Dumeril, 1805, 15 are Nearctic and 14 occur in Europe of which 8 extend to the UK. Nebriini Laporte, 1834 includes the majority of the species, more than 500, in at least 5 genera and is Holarctic extending into the Oriental region. Leistus Frölich, 1799 includes about 190 species in at least 6 subgenera and is Holarctic although only 3 species are native to the Nearctic region; 36 occur in Europe of which 8 extend to the UK. Nippononebria Ueno, 1953, formerly classified in Nebria, includes 3 Nearctic and 6 eastern Palaearctic species. The remaining species have, and in many cases remain, within the large genus Nebria Latreille, 1802; a generally - though not universally - accepted example of a subgeneric taxon raised to generic rank is Eurynebria complanata (Linnaeus, 1767) which is distinct in lacking extra-strial elytral punctures and in having multisetose penultimate labial palpomeres, but more generally there are at least 19 subgenera and more than 400 species; more than 80 occur in Europe and about 60 are Nearctic.

Ecology

Members of this subfamily occur from the Arctic circle south to North Africa, Arizona and northern parts of the Oriental region, they occur in a wide range of habitats from lowland to mountain altitudes, generally in cooler areas and many are restricted to certain habitats e.g. woodland, moorland, or marginal situations including the seashore. Adults are generally to be found resting or hunting for prey under stones or logs or among vegetation in cooler habitats, especially woodland margins and wetland marginal habitats; some high mountain species are nocturnal, searching for prey on snow fields, Eurynebria inhabits sandy beaches above the high tide-line while Nebria livida (Linnaeus, 1758) inhabits clay or sandy substrates below sea cliffs, and Nebria brevicollis (Fabricius, 1792) is among our most common carabids and might be occur almost anywhere. Species of Notiophilus Duméril, 1806 are diurnal as well as nocturnal predators and are often to be seen running on pathways etc. in bright sun while members of the genus Leistus will need to be searched for under logs etc. and are specialist springtail predators with mouthparts adapted for the role. Pelophila borealis (Paykull, 1790) is a very local insect occurring in marginal habitats in low mountain altitudes in the north and west of Ireland, Orkney and Shetland and possibly a single mainland Scottish locality.

Members of this subfamily, at least in the UK, are distinctive and will soon become familiar; Notiophilus and Leistus are quite unmistakable but more generally they may be recognized by the form of the pro-tibiae which lack an antennal cleaning notch and have two long apical spurs, and the complete margin to the base of the elytra. Our UK species are readily distinguished HERE.

Notiophilini Motschulsky, 1850

This small tribe includes about 50 species of the single genus Notiophilus Dumeril, 1806, the group is Holarctic extending south to North Africa and Costa Rica, 15 species occur in central Europe, of which 8 extend to the U.K., and 15 occur in the Nearctic although 2 of these, N. biguttatus (Fabricius, 1779) and N. palustris (Duftschmid, 1812) are adventive. Some species e.g. N. aquaticus (Linnaeus, 1758) are Holarctic. They are small beetles <8mm and parallel-sided, all are drab coloured from black to metallic bronze and some have a pale subapical elytral macula. All are very distinctive due to the very large and convex eyes, multi-carinate frons and wide second elytral interval, the fourth interval has at least one large puncture and there are various larger punctures towards the apex. There is a single large setiferous puncture on the frons beside each eye. They occur in a variety of habitats and many are generalists preferring open or lightly wooded and dry situations such as grassland, parks and gardens etc. they are active in bright sun and may be observed running rapidly on pathways and lawns. Some e.g. N. quadripunctatus Dejean, 1826 prefer marginal habitats, especially where these are sandy, while others e.g. N. rufipes Curtis, 1829 occur in moist and shaded situations among leaf-litter or under stones. The common and widespread N. biguttatus may occur in huge numbers on open arable land during the spring.

Leistus Frölich, 1799

This is a large Holarctic genus containing about 200 species in 6 subgenera, it is particularly diverse in Asia and only poorly represented in the Nearctic zone. 36 species occur in Europe, some of which extend into Morocco and Algeria. The largest subgenus, Evanoleistus Jedlicka, 1965, includes about 100 species distributed in Eastern Asia and is most diverse in China. Leistus s.str. includes about 50 species and is mostly Western Palaearctic although also represented in Asia. Two species of Nebrileistus Banninger, 1925 are endemic to Madeira and the Canary Islands. Pogonophorus Latreille, 1802 includes about 50 species and extends through the Palaearctic and Asian zones and includes several from Japan. Sardioleistus Perrault, 1980 includes 3 western European species and extends into northwest Africa. The genus is represented in the Nearctic by the 3 species of the native Nearctic subgenus Neoleistus Erwin, 1970 and also by the widespread Palaearctic and Asian native species L. ferrugineus (Linnaeus, 1758) which has become established.

The species are very distinctive and immediately recognizable, the main characters distinguishing them from other members of the Nebriini (and other carabids generally) are the expanded mandibles and otherwise modified mouthparts which are adapted to a specialized mode of feeding upon collembolan (etc.), when hunting they trap springtails with a ‘setal cage’ formed of stiff setae arranged around the appendages and sclerites of the anterior part of the head.

Most are medium sized carabids less than 12mm in length, elongate, rather narrow and depressed with long appendages, especially the mouthparts and antennae. The head is variously impressed and punctured around a convex vertex; eyes large, convex and usually prominent, and with the temples constricted to a distinct neck. Antennae inserted in front of the eyes; very long and slender, the basal segment robust, the second short and the remainder very elongate; segments 1-4 are glabrous and 5-11 pubescent. The mouthparts are variously adapted; mandibles acute and widely expanded laterally (hence the vernacular), and with a strong tooth on the inner margin, maxillae long and slender, hooked at the apex and with stiff setae on the lateral margins, all palps long and slender. Mentum transverse and emarginate, variously produced and notched medially and with long setae at the apex. The pronotum is transverse, sometimes strongly so (2:1), cordate; broadest near the middle and either strongly narrowed to obtuse hind angles or sinuate to perpendicular or toothed hind angles. Disc generally glabrous and raised, the anterior and basal areas punctured, and the lateral margins narrowly to broadly explanate and finely bordered, sometimes this explanate margin is distinctly punctured. Hind angles with or without a setiferous puncture. Scutellum usually small but obvious. Elytra generally narrow and somewhat parallel or only weakly curved, sometimes with a weak shoulder tooth, and with 9 well-impressed and often punctured striae, including a scutellar striole, which are complete to the apex. Interstices wider than the striae; convex and often finely punctured but lacking any larger setiferous punctures. Basal margin well-developed, the striae sometimes joined in pairs under this, lateral margins explanate, usually narrowly so. The hind wings vary considerably, even within a species, and while flight has been observed it seems to be rare. The basal pro-tarsal segments are dilated in the male. The form varies widely within the general habitus; some aspects of this are seen in the Russian alpine species L. frater Reitter, 1897, where the mouthparts are exaggerated, the head broad, the pronotum and elytra narrow and the legs very long.

Many have a restricted distribution but several widespread European species extend to the U.K. A few e.g. L. fulvibarbis Dejean, 1826, inhabit forests but this is unusual; steppe grassland habitats may host a wide diversity but in general most species live among tussocks, stones and debris in open and dry environments, and many have rather narrow microclimate requirements in the top few centimetres of soil or substrate. Some prefer dry environments but this varies and many are stenotopic. Many are known from only a few specimens.